[brazen1]

I read somewhere in the forum that Kodi is able to play 3D MKV without external player. Is this right?
Yes, KODI will play 3D mkv using it's internal dvdplayer.

With an 3D-MKV extracted from the original "Edge of Tomorrow":
- Still not playing inside Kodi.
- File opened with PDVD directly outside Kodi:
All 3D mkv files play default using KODI internal dvdplayer. Copy codes and instructions exactly. KODI settings as well.

Setup by brazen1's guide:
- 3D ISO is playing fine.
- But 2D ISOs are played through PDVD too.
Code is designed to play 2D iso's with PDVD by default for reasons described in guide. If you would like to play 2D iso's using KODI internal dvdplayer, simply bring up context menu when focused on the title by pressing 'C' or whatever means you access context menu and select 'dvdplayer'.

--- Video is heavily stuttering, while ISO playing with PDVD inside Kodi is OK.
Then you have wrong PDVD settings. Using code exactly as provided, there is no stuttering with either player nor with file extensions.

If you would like all 2D iso's to always default play using KODI internal dvdplayer, change this line of code in playercorefactory.xml:

From this
<rule filetypes="iso|bdmv|mpls|m2ts" player="2D"/>

to this
<rule filetypes="iso|bdmv|mpls|m2ts" player="dvdplayer"/>

Not recommended.